As part of the “Waking the Vatican” tour, one can enjoy the Sistine Chapel with a few dozen other visitors. This is a marvelous experience, seeing the work of Michaelangelo in an almost private moment. As large as the chapel is, it does feel private. Here’s a video showing the chapel.
Amazing. Seriously. If you have the opportunity, I highly recommend this experience. Do your homework about the art and history of the place in order to get the most out of it. Linger as long as possible.